A copy instruction executed by a functional-level instruction-set computing (FLIC) processor copies a variable-length data block from one resource to another resource through a cross-bar switch. Resources include general-purpose registers, input, output, and execution buffers, DRAM, SRAM, and other memory. A copy-with-validate instruction has an operand pointing to a first rule in an immediate rule table. The first rule controls validation of a first data-item in the data being copied. Validation includes range and equality checking of the data-item. The value of the data-item or the current offset can be written to a register. A format field in the rule indicates the size of the data-item, or the size is read from the data-item for variable-size formats. The current offset is incremented by the size. The next data-item is validated by a next rule, and other rules in the immediate table control validation of other data-items in the data block.